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  • 84 Chev C10 Engine Swap

    Greetings to all...
    I am building an 84 Chevy C10 short bed to drive yearly from Ohio to Florida. Not going to haul much other than a few suitcases, hand tools, and fishing poles - no heavy towing. Looking to get reliability and decent gas mileage. Considering engine swap. Have excellent, strong, low mi, 305 from '86 Pontiac Grand Prix (GP). The '84 C10 came with 305, automatic 3 speed, and 2.73 gears - but now has early 350 of unknown quality. Question is: "Will the '86 GP 305 bolt up to the '84 C10's stock transmission, motor mounts, and exhaust manifolds?" Has anyone made this or a similar swap? ('88 Hollander manual does not show this as a "complete engine" interchange.)
    Thanks for interest and replies.
    fudggj

  • #2
    Re: 84 Chev C10 Engine Swap

    I think that Chevy has a different bolt pattern for the transmission than Pontiac, but I don't know about the motor mounts.

    2002 ECLB Silverado 2500HD Duramax
    2003 ECSB Silverado 2500HD 6.0/ 4L80e totalled
    1985 RCSB C10 TBI 350/ 700r4

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    • #3
      Re: 84 Chev C10 Engine Swap

      Everything should bolt right up to the 305 from the 350. The 1986 305 should be a corporate chevy engine, not Pontiac.
      2003 GMC 1500HD - 6.0L, 4L80E, All Stock
      1986 Chevy C10 - Twin Turbo 383, 4L80E, Currently under the knife for body work.

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      • #4
        Re: 84 Chev C10 Engine Swap

        It's true, the Pontiac GP 305 for 1986 had the same 3.75 bore and 3.48 stroke as the other 305's...

        It's personal preference, but I wouldn't waste my time with the Pontiac 305... At best it was 165 hp (new) in a car that weighed only 3,200-3,300 lbs., and they were slow.

        If you're going for fuel economy and reliability I'd go with a 4.3 V6 engine. Fairly new Vortec 4.3's go for almost nothing and can be setup with a carb-friendly intake. The V6 would have more power and torque than the 305, while getting better mileage.

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        • #5
          Re: 84 Chev C10 Engine Swap

          Do not put a 4.3 V6 in a full size truck, you will not net any better MPG and the 4.3 will have to work that much harder. 305 will be fine and add a TBI set up with Megasquirt to make a great traveling combo. Dropping the tailgate down while on the freeway doesn't help fuel mileage either.

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          • #6
            Re: 84 Chev C10 Engine Swap

            The 305 should be a direct drop-in. Make sure you use the distributor that is currently on your truck. Don't over-carb it either. 600 CFM will be more than adequate.

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            • #7
              Re: 84 Chev C10 Engine Swap

              Thanks for all replies thus far - all replies were appreciated. I wonder "Will I have to drill and tap the bosses on the Grand Prix 305 block to accomodate the C-10 truck motor mounts?" (Or are the corporate Chevy 305 blocks predrilled with extra holes at the motor plant to accomodate multiple motor mount applications?)
              Last edited by fudggj; 07-12-2006, 02:01 PM.

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              • #8
                Re: 84 Chev C10 Engine Swap

                Originally posted by fudggj
                Thanks for all replies thus far - all replies were appreciated. I wonder "Will I have to drill and tap the bosses on the Grand Prix 305 block to accomodate the C-10 truck motor mounts?" (Or are the corporate Chevy 305 blocks predrilled with extra holes at the motor plant to accomodate multiple motor mount applications?)

                305 should have the standard chevrolet holes on either side of block to mount on various frames.

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                • #9
                  Re: 84 Chev C10 Engine Swap

                  correct me if i am wrong, but wont it be more work than it is worth to switch from a chevy motor to a ponti? the mounts will be different for one. i would go with a straight 6, plent of power, better fuel economy
                  90 1500 sport stock, tbichips.com hot chip on the way

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                  • #10
                    Re: 84 Chev C10 Engine Swap

                    pontiacs of that era used chevy engines

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                    • #11
                      Re: 84 Chev C10 Engine Swap

                      Many GM 5.0L engines in the 80s and early 90s were not Chevrolet 305 CID; rather, they were Oldsmobile 5.0L 307 CID.

                      The easiest way to tell if it's an Oldsmobile engine is to look for the oil fill lid. Is it on a valve cover or in the front of the engine in a stand-alone filler tube sort of setup?

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                      • #12
                        Re: 84 Chev C10 Engine Swap

                        For the "305" motor I have, the oil fill is in the valve / rocker arm cover.
                        Thanks for replies...

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                        • #13
                          Re: 84 Chev C10 Engine Swap

                          It has the chevy 305
                          " Patton said it best " Wars are not won by dying for your country, wars are won by making the other poor son of a b#### die for his country! "

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                          • #14
                            Re: 84 Chev C10 Engine Swap

                            305 - 165HP
                            262 - 150HP <--- that is the 4.3L V6. My '86 came with that.

                            The fullsize 4.3L w/ 2.73 gears yielded a max of 19mpg. My truck did very well with that, considering a TH400 was behind it. Pulled that all out in 2000 b/c I ran it hot with a blown head gasket. A direct replacement went in, and I put 49,900 on it before it sat for a year. Those weren't high HP motors, but TQ was a different story.

                            Personally, 350s are a dime-a-dozen here in La. Not to mention aftermarket is enormous. Good luck with whatever you decide to do.
                            Last edited by BlackC10; 07-15-2006, 07:55 PM.
                            5.3L '86 Silverado C10

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                            • #15
                              Re: 84 Chev C10 Engine Swap

                              Originally posted by fudggj
                              For the "305" motor I have, the oil fill is in the valve / rocker arm cover.
                              Thanks for replies...
                              by all means, use the 305 then....you'll be happier with the extra 2 cylinders in the heavier truck. Also look into the Holley 2 barrel fuel injection either with the Holley fuel controller or the Megasquirt controller and tune for maximum MPG. My mom's 91 camaro came with a 305 and TBI, engine ran great and netted about 25MPG.

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